(a) Field of the Invention
The present invention relates to a protocol embodying system and method in the GGSN. More specifically, the present invention relates to a protocol embodying system and method in the GGSN for performing routing by using an IP layer.
(b) Description of the Related Art
The GGSN (gateway GPRS supporting node) represent a node for linking a GPRS internal network and an external public network in the GPRS (general packet radio service.) All the packets transmitted by a mobile station are provided to the external network through the GGSN, and all the packets on the external network are transmitted to the mobile station through the GGSN.
Therefore, the GGSN functions as a gateway for performing routing between the internal network and the external network.
FIG. 1 shows a stack of an inner protocol of the GGSN.
As shown in FIG. 1, the stack of an inner protocol of the GGSN is classified as a part for the GPRS network and a part for the PDN (public data network), and the upper IP (Internet protocol) located between the GPRS network and the PDN performs the routing function between the two networks.
First, as to the protocol configuration of the part of the GPRS network, the GTP (GPRS tunneling protocol)-U is a protocol for tunneling user packets and transmitting and receiving them in the GPRS network.
The GTP-U uses the UDP (user datagram protocol) for a lower transmit layer protocol, and uses a lower IP for network layers GPRS-L1 (layer 1) and GPRS-L2 (layer 2).
The GPRS-L1 and GPRS-L2 are configured according to the connected GPRS network, and the ATM (asynchronous transfer mode) or the frame relay is generally used.
The protocol on the PDN side is configured only with the PDN-L1 and PDN-L2 since they are IP packets and can be transmitted with the protocols of the first and second layers L1 and L2 without support of a special protocol when the tunneling is canceled in the GTP-U.
The PDN-L1 and PDN-L2 are configured according to the configuration of the PDN, and an Ethernet interface is generally used so that they may be connected to an edge router.
Data D1 transmitted from the GPRS network is a GTP message tunneled by the GTP. That is, D1 is transmitted to the lower IP through the protocols of the network layer, that is, GPRS-L1 and GPRS-L2, is provided to the GTP-U through the transfer layer protocol used by the GTP, that is, the UDP, and then becomes the GTP message.
After this, the tunneling on the GTP message is canceled by the GTP-U, the GTP message is converted into the IP packet, and the IP packet is transmitted to the upper IP for the purpose of routing. The upper IP performs routing according to the Internet routing rule, transmits the packet to the PDN-L2 which connects the PDNs when an arrival address of the packet is given to a node on the PDN, and the packet is finally provided to the outside through PDN-L1.
It is therefore known from the above description that two IP layers are provided in order to connect the GPRS network and the PDN.
The lower IP layer functions as a protocol of the network layer for transmitting the GTP message, and the upper IP layer functions as a protocol of the network layer for routing the IP packet that is passed through the tunnel.
That is, the lower IP processes the GTP message and the upper IP processes the IP packet while the two IPs are concurrently provided in a single system.
The two IP layers have the same performance procedure and logic even through they respectively process the GTP message and the IP packet.
Further, the IP layer is managed in the so-called stateless format that manages no status of user instances. Therefore, it may increase complexity of the system to embody two IP layers in a single system.
As described above, it is needed for the stack of the inner protocol of the conventional GGSN to separately process two IP layers in order to perform a process for outputting the data Dl transmitted from the GPRS network to the outside.
Accordingly, the prior art problematically increases the complexity since two IP blocks managed in the stateless status are embodied when the GGSN performs routing between the GPRS network and the PDN.